Alignment apparatus for use in hip arthroplasty

ABSTRACT

Hip arthroplasty apparatus and methods are described to determine an orientation of an acetabular cup impactor, the acetabular cup impactor being moveable to a desired orientation relative to a patient&#39;s pelvic region for implantation of an acetabular cup. In one embodiment an electronic orientation sensor is transitionable between a first location on the patient&#39;s pelvic region and a second location on the acetabular cup impactor. At the first location, the orientation sensor is adapted to record a reference orientation of the patient&#39;s pelvic region. At the second location the orientation sensor is adapted to determine an orientation of the acetabular cup impactor relative to the reference orientation.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Australian ProvisionalPatent Application No. 2013903947 filed on 14 Oct. 2013 and fromAustralian Provisional Patent Application No. 2014900142 filed on 17Jan. 2014, the contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to alignment apparatus for use in hiparthroplasty.

BACKGROUND

Hip arthroplasty includes surgical procedures in which the hip joint isreplaced by a prosthetic implant. The prosthetic implant can consist ofdifferent parts, including an acetabular cup designed to locate in theacetabulum (hip socket). The acetabular cup is located in position usingan acetabular cup impactor, which generally takes the form of anelongate rod, having the cup at one end, and which is used to insert andorient the cup in the acetabulum. To ensure that an acetabular cupfunctions correctly, and does not wear significantly or cause damage toa patient, it is important that the cup is oriented and positionedcorrectly in the acetabulum.

Any discussion of documents, acts, materials, devices, articles or thelike which has been included in the present specification is not to betaken as an admission that any or all of these matters form part of theprior art base or were common general knowledge in the field relevant tothe present disclosure as it existed before the priority date of eachclaim of this application.

SUMMARY

Various aspects of the present disclosure provide apparatus, andmethods, for use in hip arthroplasty, where an acetabular cup impactoris used to implant an acetabular cup at the acetabulum of a patient'spelvic region. A device can be mounted on the acetabular cup impactorand/or the patient's pelvic region and adapted to sense relative angulardisplacement of the impactor and pelvic region in order to assist withguidance of the acetabular cup impactor to a desired orientation.

According to one aspect, the present disclosure provides hiparthroplasty apparatus comprising:

an acetabular cup impactor moveable to a desired orientation relative toa patient's pelvic region for implantation of an acetabular cup; and

an electronic orientation sensor transitionable between a first locationon the patient's pelvic region and a second location on the acetabularcup impactor;

wherein, at the first location, the orientation sensor is adapted torecord a reference orientation of the patient's pelvic region, and atthe second location the orientation sensor is adapted to determine anorientation of the acetabular cup impactor relative to the referenceorientation.

According to another aspect, the present disclosure provides a method ofpositioning an acetabular cup impactor, comprising:

locating an electronic orientation sensor at a first location on apatient's pelvic region, using the electronic orientation sensor locatedat the first location to record a reference orientation of the patient'spelvic region, transitioning the electronic orientation sensor from thefirst location to a second location on an acetabular cup impactor, theacetabular cup impactor being moveable to a desired orientation relativeto the patient's pelvic region for implantation of an acetabular cup,and using the orientation sensor located at the second location todetermine an orientation of the acetabular cup impactor relative to thereference orientation.

According to yet another aspect, the present disclosure provides anelectronic orientation sensor, the sensor being transitionable from afirst location on a patient's pelvic region to a second location on anacetabular cup impactor, the acetabular cup impactor moveable to adesired orientation relative to a patient's pelvic region forimplantation of an acetabular cup, wherein, at the first location, theorientation sensor is adapted to record a reference orientation of thepatient's pelvic region, and at the second location the orientationsensor is adapted to determine an orientation of the acetabular cupimpactor relative to the reference orientation.

According to another aspect, the present disclosure provides a method ofdetermining an orientation of an acetabular cup impactor, comprising:

recording a reference orientation of a patient's pelvic region using anelectronic orientation sensor located at a first location on thepatient's pelvic region, and determining an orientation of an acetabularcup impactor relative to the reference orientation, using the electronicorientation sensor, when the electronic orientation sensor is located ata second location on the acetabular cup impactor after beingtransitioned to the second location from the first location, theacetabular cup impactor being moveable to a desired orientation relativeto the patient's pelvic region for implantation of an acetabular cup.

According to yet another aspect, the present disclosure providessoftware that, when installed on a computing device, causes thecomputing device to perform the method of the immediately precedingaspect.

In one embodiment, the orientation sensor is mounted or adapted to bemounted on the acetabular cup impactor, e.g. at a distal end of a handleof the impactor, via releasable fixation means. The apparatus maycomprise a mount that is configured to engage both the orientationsensor and the impactor and releasably fix the positions of theorientation sensor and the impactor relative to each other. The mountmay include two clamp portions, for example, adapted to clamp to theorientation sensor and the impactor, respectively. Similarly, theorientation sensor may be mounted or adapted to be mounted on the pelvicregion via releasable fixation means. The apparatus may comprise a mountthat is configured to engage both the orientation sensor and the pelvicregion and releasably fix the positions of the orientation sensor andthe pelvic region relative to each other. The mount may include twoclamp portions, for example, adapted to clamp to the orientation sensorand the pelvic region, respectively. Generally, when located at thefirst or second location, on the pelvic region and impactor,respectively, the orientation sensor may or may not directly contact thepelvic region or impactor. However, the orientation of the orientationsensor may be substantially fixed relative to the pelvic region orimpactor.

The orientation sensor may be adapted to determine the orientation ofthe acetabular cup impactor relative to the reference orientation inthree-dimensional space. The relative orientation of the longitudinalaxis of the handle and shaft of the acetabular cup impactor may bedetermined. Relative orientation may be determined as a degree ofrelative rotation about three orthogonal axes of a coordinate system(e.g. as Euler angles or otherwise). The reference orientation mayprovide for a local coordinate system.

The orientation sensor may determine changes in orientation based ongravitational fields, magnetic fields, and/or acceleration, for example.The orientation sensor may calculate the orientation of the impactorwith respect to the specified reference orientation through monitoringof degrees of rotation about multiple axes as it transitions from thefirst location on the pelvic region to the second location on theimpactor and as it moves during any subsequent movement of the impactor.The orientation sensor may comprise one or more of a gyroscope, amagnetic field sensor, an accelerometer, angular position sensor, and/orrotary sensor and/or one or more other types of movement or absolute orrelative position sensors.

The apparatus and/or orientation sensor may comprise an output deviceadapted to provide information about the relative orientation of theimpactor and/or the reference orientation to a clinician or other user,e.g. via text, graphics, audio and/or tactile feedback. The outputdevice may comprise a display, speaker and/or vibrator, for example.

The apparatus and/or orientation sensor may comprise a processor adaptedto determine the reference orientation and/or the relative orientationof the impactor relative to the reference orientation.

The apparatus and/or orientation sensor may comprise an input deviceadapted to receive an input from the clinician or other user. The inputdevice may include one or more buttons, a keyboard, a touch sensitivescreen, voice detector or otherwise. The input device may receive inputfrom the user about a desired orientation of the impactor, e.g. desiredanteversion and/or inclination angles, and/or measured orientation data,e.g. measured anteversion and/or inclination angles. The input devicemay receive input from the user indicative of when the orientationsensor is located on the pelvic region. The providing of an input thatis indicative of when the orientation sensor is located on the pelvicregion may trigger recording of the reference orientation by theorientation sensor.

The desired orientation of the impactor may correspond to an optimumimplantation orientation of the acetabular cup. The optimum orientationcan be defined by angles of inclination (abduction) and/or anteversion,for example. The desired orientation may be a desired angle ofanteversion or a desired angle of inclination or a desired combinationof anteversion and inclination angles. Anteversion and inclinationangles can be defined differently, depending on whether anatomic,radiographic or operative reference frames are used. In discussionsherein, desired and measured anteversion and inclination angles aredefined in respect of the anatomic reference frame unless indicatedotherwise. Nevertheless, the techniques described are not limited tousing angles defined with respect to this reference frame only.

The desired orientation of the impactor may depend on surgicalcircumstances including the anatomy of the patient and preferences ofthe surgeon. A commonly desired anteversion angle is about 20° and acommonly desired inclination angle is about 45°. Nevertheless, thedesired anteversion may be anywhere between −35° and 60°, or 0° and 40°,for example, and the desired inclination may be anywhere between 25° and60°, or 35° and 50, for example.

In one embodiment, any one or more of the orientation sensor, theprocessor, the input device and the output device may be comprised in asingle electronic device, such as a smartphone, tablet computer, orsimilar. The electronic device may run a software program or software“app” adapted to control one or more of these elements.

While an electronic orientation sensor can be used to determineorientation of an acetabular cup impactor as discussed above, anelectronic orientation sensor may also be used to monitor changes inorientation in the pelvic region during surgery.

In particular, according to one aspect, the present disclosure provideship arthroplasty apparatus comprising an electronic orientation sensorlocatable on a patient's pelvic region, wherein the orientation sensoris adapted to record a reference orientation of the patient's pelvicregion and subsequently monitor changes in orientation of the pelvicregion relative to the reference orientation.

According to another aspect, the present disclosure provides a method ofmonitoring changes in orientation of a pelvic region during surgery,comprising:

locating an electronic orientation sensor on a patient's pelvic regionand using the electronic orientation sensor to record a referenceorientation of the patient's pelvic region, using the orientation sensorto monitor changes in orientation of the pelvic region relative to thereference orientation.

According to yet another aspect, the present disclosure provides anelectronic orientation sensor, the sensor being locatable on a patient'spelvic region where it is adapted to record a reference orientation ofthe patient's pelvic region and monitor changes in orientation of thepelvic region relative to the reference orientation.

According to another aspect, the present disclosure provides a method ofmonitoring changes in orientation of a pelvic region during surgery,comprising:

recording a reference orientation of a patient's pelvic region using anelectronic orientation sensor located on the patient's pelvic region,and monitoring changes in the orientation of the pelvic region relativeto the reference orientation.

According to yet another aspect, the present disclosure providessoftware that when, installed on a computing device, causes thecomputing device to perform the method of the immediately precedingaspect.

The orientation sensor may be configured as described above with respectto earlier aspects. The apparatus and/or orientation sensor may comprisean output device and/or an input device as described above with respectto earlier aspects.

Monitoring of changes in the orientation of the pelvic region may beused independently of or in conjunction with determining the orientationof the acetabular cup impactor as described with respect to earlieraspects.

In general, a pelvic region can move during surgery and this can imparterror into the procedure in which the orientation of the acetabular cupimpactor is determined relative to a reference orientation of the pelvicregion. In effect, movement of the pelvic region can cause the recordedreference orientation to be inaccurate. By monitoring changes in theorientation of the pelvic region, correction can be applied. In oneembodiment, an orientation sensor is located on the pelvic region andanother orientation sensor, after having recorded the referenceorientation of the pelvic region, is located on the acetabular cupimpactor. The orientation sensor located on the pelvic region is adaptedto communicate, e.g., wirelessly or otherwise, with the orientationsensor located on the acetabular cup impactor to provide informationabout changes in the orientation of the pelvic region, allowingcorrection of a recorded reference orientation to be made. Correctionmay be made substantially in ‘real-time’.

Various other aspects of the present disclosure also provide apparatus,and methods, for use in hip arthroplasty, in which an acetabular cupimpactor is used to implant an acetabular cup at the acetabulum of apatient's pelvic region. An image capture device can be mounted on oneof the acetabular cup impactor and the patient's pelvic region andadapted to capture images of the other of the acetabular cup impactorand pelvic region. The images can be presented on a display and caninclude one or more indicia, e.g., markers. Through observation of theone or more indicia in the images, the acetabular cup impactor can beguided to a desired orientation.

According to one aspect, the present disclosure provides hiparthroplasty, apparatus comprising:

an image capture device adapted to mount on one of an acetabular cupimpactor and a patient's pelvic region, the acetabular cup impactorbeing moveable to a desired orientation relative to the patient's pelvicregion for implantation of an acetabular cup, wherein the image capturedevice is adapted to capture images of the other of the acetabular cupimpactor and the patient's pelvic region, including one or more firstmarkers positioned on that other of the acetabular cup impactor andpelvic region;

a display device connected to the image capture device and adapted todisplay images captured from the image capture device; and

a processor adapted to cause overlay of one or more second markers inthe images displayed by the display device such that, when one or moreof the first markers shown in the displayed images are substantiallyaligned with one or more of the second markers overlaid in the displayedimages, the acetabular cup impactor is oriented in the desiredorientation.

According to another aspect, the present disclosure provides a method ofpositioning an acetabular cup impactor, comprising:

mounting an image capture device on one of an acetabular cup impactorand a patient's pelvic region, the acetabular cup impactor beingmoveable to a desired orientation relative to the patient's pelvicregion for implantation of an acetabular cup;

using the image capture device to capture images of the other of theacetabular cup impactor and the patient's pelvic region, including oneor more first markers positioned on that other of the acetabular cupimpactor and pelvic region;

displaying the images captured from the image capture device on adisplay device connected to the image capture device; and

overlaying one or more second markers in the images displayed by thedisplay device such that, when one or more of the first markers shown inthe displayed images are substantially aligned with one or more of thesecond markers overlaid in the displayed images, the acetabular cupimpactor is oriented in the desired orientation.

In one embodiment, the image capture device is mounted or adapted to bemounted on the acetabular cup impactor, and the image capture device isadapted to capture images of the patient's pelvic region, including oneor more first markers positioned at the patient's pelvic region. Theapparatus may comprise a mount that is configured to engage both theimage capture device and the impactor and releasably fix the positionsof the image capture device and the impactor relative to each other. Themount may include two clamp portions, for example, adapted to clamp tothe image capture device and the impactor, respectively.

In this embodiment, the one or more first markers may comprise one ormore anatomical landmarks. For example, the one or more anatomicallandmarks may comprise one or both of the anterior superior iliacspines. In one embodiment, the one or more first markers comprise avector line extending between anterior superior iliac spines. The vectorline may be an imaginary line between the anterior superior iliac spinesor may be a line that is drawn on the patient's pelvic region.Alternatively, the vector line may be a line that is drawn on, orprovided by an edge, channel or visual feature, of a marker element,e.g. a rod, bar or other device, which is connected to or positionedadjacent the pelvis.

The apparatus may comprise a tilt sensor. The tilt sensor may be fixedin relation to the acetabular cup impactor and/or the image capturedevice. The tilt of the impactor and/or image capture device can bedetermined as the image capture device moves, e.g. as a result of movingthe acetabular cup impactor. The tilt may be measured relative to ahorizontal plane, for example.

The image capture device, in addition to any one or more of the displaydevice, the processor and the tilt sensor, may be comprised in a singleelectronic device, such as a smartphone, tablet computer, or similar.The electronic device may run a software program or software “app”adapted to control the display device, processor and/or tilt sensor inaccordance with the apparatus and methods of the present disclosure.

The mount of the apparatus may be adapted to engage both the electronicdevice and the impactor and releasably fix the positions of theelectronic device and the impactor relative to each other. The mount mayinclude two clamp portions, for example, adapted to clamp to theelectronic device and the impactor, respectively.

The desired orientation of the impactor may correspond to an optimumimplantation orientation of the acetabular cup. The optimum orientationcan be defined by angles of inclination (abduction) and/or anteversion,for example. The desired orientation may be a desired angle ofanteversion or a desired angle of inclination or a desired combinationof anteversion and inclination angles.

The processor may be adapted to receive orientation data related to theimpactor. The orientation data may include desired orientation of theimpactor, e.g. desired anteversion and/or inclination angles, and/ormeasured orientation data, e.g. measured anteversion and/or inclinationangles. Based on the received orientation data, the processor maydetermine appropriate positions and/or orientations for the one or moresecond markers displayed in the images. A commonly desired anteversionangle is about 20° and a commonly desired inclination angle is about45°. Nevertheless, depending on circumstances including the anatomy ofthe patient and preferences of the surgeon, the desired anteversion maybe anywhere between 0° and 40°, or even −35° and 60°, and the desiredinclination may be anywhere between 35° and 50, or even 25° and 60°.

According to one aspect, the present disclosure provides a method ofguiding the positioning of an acetabular cup impactor in a hiparthroplasty procedure, the method being adapted for use with hiparthroplasty apparatus that comprises:

an image capture device adapted to mount on one of an acetabular cupimpactor and a patient's pelvic region, the acetabular cup impactorbeing moveable to a desired orientation relative to the patient's pelvicregion for implantation of an acetabular cup, wherein the image capturedevice is adapted to capture images of the other of the acetabular cupimpactor and the patient's pelvic region, including one or more firstmarkers positioned on that other of the acetabular cup impactor andpelvic region; and

a display device connected to the image capture device and adapted todisplay images captured from the image capture device; and

a processor adapted to cause overlay of one or more second markers inthe images displayed by the display device such that, when one or moreof the first markers shown in the displayed images are substantiallyaligned with one or more of the second markers overlaid in the displayedimages, the acetabular cup impactor is oriented in the desiredorientation,

the method comprising:

determining the position and orientation for the one or more secondmarkers to be overlaid in the images displayed by the display devicebased on received orientation data including a desired angle oforientation of the acetabular cup impactor and a measured orientationangle of the acetabular cup impactor data.

In one embodiment, the received orientation data comprises a desiredanteversion angle of the acetabular cup impactor and a measuredinclination angle of the impactor. In another embodiment, the receivedorientation data comprises a desired inclination angle of the acetabularcup impactor and a measured anteversion angle of the impactor. Inanother embodiment, the received orientation data comprises desiredanteversion and inclination angles of the acetabular cup impactor, andmeasured anteversion and inclination angles of the impactor.

In one embodiment, one or more of the measured angles may be obtained atleast in part through a feature recognition process. For example, bydetermining the positioning of one or more of the first markers in theimages, one or more of the angles of anteversion and inclination of theacetabular cup impactor may be measured.

Additionally or alternatively, the measured orientation angle may beobtained at least in part by the tilt sensor, particularly when the tiltsensor is fixed in position relative to the impactor. Since the tiltsensor may determine tilt with reference to a gravitational field,whether or not the tilt sensor provides a measured anteversion angle ormeasured inclination angle for the impactor can depend on theorientation of the patient during surgery, e.g. whether or not they arein a supine position or a lateral recumbent position.

In one embodiment, the tilt sensor may provide measurements of one ofthe anteversion angle and the inclination angle, which measurements canbe presented and continually updated on the display (or on a differentdisplay). Following from this, the second markers may be used to guideorienting of the impactor with respect to the other one of theanteversion angle and the inclination angle only. Thus, the surgeon mayorient the impactor so that it has one of the desired anteversion angleand the desired inclination angle by simply by observing changes in thedisplayed measurements from the tilt sensor and moving the impactoraccordingly, and the surgeon may orient the impactor so that it has theother of the desired anteversion angle and the desired inclination angleby aligning one or more of the first markers shown in the displayedimages with one or more of the second markers overlaid in the displayedimages.

The step of determining the positions and/or orientations for the one ormore second markers may be carried out by the processor.

In one aspect, the present disclosure provides software that causes theprocessor to perform the method of the preceding aspect. The softwaremay cause the processor to perform the method of the preceding aspectwhen installed on an electronic device comprising the processor.

As indicated, the processor may be comprised in an electronic devicesuch as a smartphone, tablet computer, laptop computer, personalcomputer or otherwise. The electronic device may comprise other featuresof the apparatus described above, such as the image capture device,display device and/or tilt sensor. The software may take the form ofapplication software (e.g. an “app”), which may be downloadable from amedia library such as iTunes™ or Android™ media libraries or otherwise.

Nonetheless, more generally, it will be recognised that processers orprocessing apparatus as disclosed herein may comprise a number ofcontrol or processing modules for controlling one or more components ofthe apparatus and may also include one or more storage elements, forstoring desired angle data, measured angle data, orientation data,and/or patient data, etc. The modules and storage elements can beimplemented using one or more processing devices and one or more datastorage units, which modules and/or storage devices may be at onelocation or distributed across multiple locations and interconnected byone or more communication links. Processing devices may include tablets,smartphones, laptop computers, person computers personal digitalassistants and other types of electronic devices, including systemsmanufactured specifically for the purpose of carrying out methodsaccording to the present disclosure.

Further, the processing modules can be implemented by a computer programor program code comprising program instructions. The computer programinstructions can include source code, object code, machine code or anyother stored data that is operable to cause the processor to perform thesteps described. The computer program can be written in any form ofprogramming language, including compiled or interpreted languages andcan be deployed in any form, including as a stand-alone program or as amodule, component, subroutine or other unit suitable for use in acomputing environment. The data storage device(s) may include suitablecomputer readable media such as volatile (e.g. RAM) and/or non-volatile(e.g. ROM, disk) memory or otherwise.

The processor may be adapted to adjust the orientation of the one ormore second markers that are overlaid in the images displayed by thedisplay device depending on the received orientation data. For example,the processor may be adapted to continually adjust the orientation ofthe one or more second markers that are overlaid in the images displayedby the display device depending on measured orientation data. The one ormore second markers may comprise lines and the orientation of the lines(the angle that the lines extend across all or part of the displayedimages) may be adjusted. In alternative embodiments, the one or moresecond markers may comprise dots, shapes, graduated shading and/orcolouring, etc.

The orientation of one or more second markers that are overlaid in theimages displayed by the display device may be at least partiallydependent on the position in the images at which they are overlaid. Forexample, if one of the second markers is to be overlaid towards a lowerregion of the image, the lower region corresponding to a part of theimage generated with respect to a lower portion or angle of the imagecapture device's field of view, the processor can be configured toorientate that second marker differently to an orientation that it wouldbe overlay one of the second markers towards a higher region of theimage, the higher region corresponding to a part of the image generatedwith respect to a higher portion or angle of the image capture device'sfield of view. The processor may be adapted to continually determine,for different positions of the image (e.g. at different distances from acentral, 0°, axis of the image capture device's field of view), anappropriate orientation for a second marker that is to be overlaid atthat position, depending on the desired and measured anteversion and/orinclination angles. Generally, this approach recognises that the fieldof view of the image capture device will necessarily cover a range ofangles and therefore the orientation of items as seen within imagescaptured by the image capture device, relative to the impactor on whichimage capture device is mounted, will partially depend on where in thefield of view of the camera those items are positioned. The processormay be adapted to determine a plurality of different second markerorientation angles for multiple positions in the images at which secondmarkers are to be overlaid, and the processor may be adapted to overlaythe plurality of second markers in the images accordingly.

In one embodiment, the patient is in a supine position. The imagecapture device and the tilt sensor are mounted on the impactor. The tiltsensor is adapted to measure anteversion angles of the impactor andcontinually provide the measured anteversion angles to the processor.The processor is also adapted to receive a data input, or ispre-programmed, with the desired inclination angle of the impactor.Based in part on the continually measured anteversion angles and thedesired inclination angle, the processor is adapted to continuallydetermine an appropriate orientation of each one of a plurality of thesecond markers that are to be overlaid over the images, for differentpositions in the images (e.g. for different distances in the image fromthe central axis of the image capture device's field of view), and theprocessor is adapted to overlay the second markers in the imagesaccordingly. Since the appropriate orientation for the second markerswill change depending on the tilt of the impactor (the measuredanteversion), the orientation of the second markers in the images maychange substantially in ‘real time’ as the surgeon moves the impactor.Meanwhile, the processor is adapted to present the measured anteversionangle on the display and continually update the display as the measuredanteversion angle changes.

In this embodiment, when at least one first marker visible in the imageis brought substantially in alignment with its nearest second marker orsecond markers, the impactor will be oriented with substantially thedesired inclination angle. At the same time, the desired anteversionangle can be achieved by observing the measured anteversion anglepresented on the display, and moving of the impactor accordingly.

In an alternative embodiment, the patient is in a lateral recumbentposition. The image capture device and the tilt sensor are mountedon/fixed to the impactor. Thus, the tilt sensor, in contrast to thepreceding embodiment, is adapted to measure inclination angles of theimpactor and continually provide measured inclination angles to theprocessor. The processor is also adapted to receive a data input, or ispre-programmed, with the desired anteversion angle of the impactor.Based in part on the continually measured inclination angles and thedesired anteversion angle, the processor is adapted to continuallydetermine an appropriate orientation of each one of a plurality of thesecond markers that are to be overlaid over the images, for differentpositions in the images (e.g. for different distances in the image fromthe central axis of the image capture device's field of view), and theprocessor is adapted to overlay the second markers in the imagesaccordingly. Since the appropriate orientation for the second markerswill change depending on the tilt of the impactor (the measuredinclination), the orientation of the second markers in the images maychange substantially in ‘real time’ as the surgeon moves the impactor.Meanwhile, the processor is adapted to present the measured inclinationangle on the display and continually update the display as the measuredinclination angle changes.

In this embodiment, when at least one first marker visible in the imageis brought substantially in alignment with its nearest second marker orsecond markers, the impactor will be oriented with substantially thedesired anteversion angle. At the same time, the desired inclinationangle can be achieved by observing the measured inclination anglepresented on the display, and moving of the impactor accordingly.

In an alternative embodiment, the image capture device is mounted oradapted to be mounted on the pelvic region, e.g. on the pelvic bone, andthe image capture device is adapted to capture images of the acetabularcup impactor, including one or more first markers positioned on theacetabular cup impactor. The apparatus may comprise a mount that isconfigured to engage both the image capture device and the pelvic regionand releasably fix the positions of the image capture device and thepelvic region. The mount may include two clamp portions, adapted toclamp to the image capture device and the pelvic region, respectively.

In this embodiment, the one or more first markers may comprise one ormore features of the acetabular cup impactor and/or one or morenavigation elements attached to the acetabular cup impactor. Forexample, the impactor may be generally elongate and may define alongitudinal axis and the one or more first markers comprise a vectorline extending along the longitudinal axis. The vector line may be animaginary line, a line that is drawn on the impactor, or a line providedby an edge, channel or other visual feature of the impactor.Additionally or alternatively, other types of markers may be used. Forexample, one or more circles, part-circles, ellipses, part-ellipses,spheres or other shapes may be provided in fixed positions relative tothe impactor. Where a plurality of first markers is provided, themarkers may be positioned at different distances along the longitudinalaxis of the impactor, for example.

This embodiment may differ from one or more of the embodiments describedpreviously in that it may not make use of a tilt sensor to continuallydetermine one of the anteversion and inclination angles. Particularlywhen the image capture device and the tilt sensor are integrated into asingle device, since the image capture device is mounted to the pelvicregion, which remains substantially stationary relative to thegravitational field when the impactor is moved, a tilt sensor may be notbe available for monitoring changes in anteversion or inclination of theimpactor. Nonetheless, the tilt sensor may be used to determine theorientation of the pelvis, before, during and/or after surgery, as analignment tool.

A calibration procedure may be employed in order to determine anappropriate position for one or second markers to be overlaid on thedisplayed images, such that when one or more of the first markers shownin the displayed images are substantially aligned with one or more ofthe second markers overlaid in the displayed images, the acetabular cupimpactor is oriented in the desired orientation. The calibrationprocedure may be carried out to determine, generally, the pivot point ofthe impactor relative to the image capture device, the length of theimpactor and/or the positions of the one or more markers on theimpactor. Based on these details, the processor may determine where theone or more second markers should be overlaid in the images to guidepositioning of the impactor to the desired orientation.

The calibration procedure may be performed with the impactor andacetabular cup engaged in the hip socket of the pelvic region and/orperformed remotely from the pelvic region.

During the calibration procedure, the processor may overlay one or morethird markers on the images, which third markers indicate one or morepositions at which one or more of the first markers should be locatedduring the calibration procedure. When positioned accordingly, a useraction may be required to provide further information to the processor.For example, when one of the first markers is aligned with one of thethird markers, a user may be required to identify on the display thelocation of a different one of the first markers and/or the location ofthe shaft of the impactor. The identification may be performed bytouching the display (if a touch screen display is used) or moving and‘clicking’ a visible cursor in the image. This process of alignment witha third marker and subsequent location identification may be repeatedmultiple times (e.g. 2, 3, 4 or more times), but with the one or morethird markers positioned differently in the images in each instance.

In some embodiments, second markers may not be overlaid over the imagesand other types of indicia may be used. Indicia representing both theanteversion and inclination angles of the impactor may be displacedsubstantially in ‘real time’ on the display, for example, enabling asurgeon to move the impactor to the desired orientation based onobservation of changes to the displayed angles.

Following from this, according to a one aspect, the present disclosureprovides hip arthroplasty, apparatus comprising:

an image capture device adapted to mount on one of an acetabular cupimpactor and a patient's pelvic region, the acetabular cup impactorbeing moveable to a desired orientation relative to the patient's pelvicregion for implantation of an acetabular cup, wherein the image capturedevice is adapted to capture images of the other of the acetabular cupimpactor and the patient's pelvic region, including one or more firstmarkers positioned on that other of the acetabular cup impactor andpelvic region;

a display device connected to the image capture device and adapted todisplay images captured from the image capture device; and

a processor adapted to provide one or more indicia in the imagesdisplayed by the display device to guide the acetabular cup impactor tothe desired orientation.

According to another aspect, the present disclosure provides a method ofpositioning an acetabular cup impactor, comprising:

mounting an image capture device on one of an acetabular cup impactorand a patient's pelvic region, the acetabular cup impactor beingmoveable to a desired orientation relative to the patient's pelvicregion for implantation of an acetabular cup;

using the image capture device to capture images of the other of theacetabular cup impactor and the patient's pelvic region, including oneor more first markers positioned on that other of the acetabular cupimpactor and pelvic region;

displaying the images captured from the image capture device on adisplay device connected to the image capture device; and

providing one or more indicia in the images displayed by the displaydevice to guide the acetabular cup impactor to the desired orientation.

According to yet another aspect, the present disclosure provides amethod of guiding the positioning of an acetabular cup impactor in a hiparthroplasty procedure, the method being adapted for use with hiparthroplasty apparatus that comprises:

an image capture device adapted to mount on one of an acetabular cupimpactor and a patient's pelvic region, the acetabular cup impactorbeing moveable to a desired orientation relative to the patient's pelvicregion for implantation of an acetabular cup, wherein the image capturedevice is adapted to capture images of the other of the acetabular cupimpactor and the patient's pelvic region, including one or more firstmarkers positioned on that other of the acetabular cup impactor andpelvic region; and

a display device connected to the image capture device and adapted todisplay images captured from the image capture device; and

a processor adapted to provide one or more indicia in the imagesdisplayed by the display device to guide the acetabular cup impactor tothe desired orientation,

the method comprising:

determining an orientation of the acetabular cup impactor data based atleast on a positioning of the one or more first markers in the images;and

based on the determined orientation, providing one or more indicia inthe images displayed by the display device to guide the acetabular cupimpactor to the desired orientation.

Throughout this specification the word “comprise”, or variations such as“comprises” or “comprising”, will be understood to imply the inclusionof a stated element, integer or step, or group of elements, integers orsteps, but not the exclusion of any other element, integer or step, orgroup of elements, integers or steps.

BRIEF DESCRIPTION OF DRAWINGS

By way of example only, embodiments are now described with reference tothe accompanying drawings, in which:

FIG. 1 shows apparatus according to an embodiment of the presentdisclosure with an electronic device at a first location;

FIG. 2 shows the apparatus of FIG. 1 with the electronic device at asecond location;

FIG. 3 shows a schematic view of elements of the electronic device ofFIG. 1;

FIG. 4 shows a pelvic calibration display screen from the electronicdevice of FIG. 1;

FIG. 5 shows an impactor orientation display screen from the electronicdevice of FIG. 1;

FIG. 6 shows a display screen from an electronic device used in anotherembodiment of the present disclosure; and

FIG. 7 shows apparatus according to another embodiment of the presentdisclosure.

FIG. 8 shows apparatus according to another embodiment of the presentdisclosure;

FIG. 9 shows an image of a pelvic region captured by a camera of theapparatus of FIG. 8;

FIG. 10 shows a schematic view of elements of an electronic device usedin the apparatus of FIG. 8;

FIG. 11 shows an outline of the area covered by the image of FIG. 9,with guidelines positioned at different locations in the area, theguidelines being indicative of positions in the area that correspondingto 10° intervals within the field of view of the camera;

FIG. 12 shows a plurality of marker lines, each positioned withreference to one of the guidelines of FIG. 11, the marker lines beingfor guiding positioning of an acetabular cup impactor of the apparatusof FIG. 8;

FIG. 13 shows the plurality of marker lines of FIG. 12 overlaid on theimage of FIG. 9, with the acetabular cup impactor in a first positionrelative to the pelvic region;

FIG. 14 shows the plurality of marker lines of FIG. 12 overlaid on theimage of FIG. 9, with the acetabular cup impactor in a second positionrelative to the pelvic region;

FIG. 15 shows apparatus according to another embodiment of the presentdisclosure;

FIG. 16 shows an image of an acetabular cup impactor captured by acamera of the apparatus of FIG. 15;

FIG. 17 shows a schematic view of elements of an electronic device usedin the apparatus of FIG. 15;

FIGS. 18a to 18d show calibration markers overlaid on images captured bythe camera of the apparatus of FIG. 15;

FIG. 19 shows an alignment marker overlaid on an image captured by thecamera of the apparatus of FIG. 15;

FIG. 20 shows apparatus according to another embodiment of the presentdisclosure;

FIG. 21 shows an image of an acetabular cup impactor captured by acamera of the apparatus of FIG. 20;

FIGS. 22a to 22d show calibration markers overlaid on images captured bythe camera of the apparatus of FIG. 20;

FIG. 23 shows an alignment marker overlaid on an image captured by thecamera of the apparatus of FIG. 20.

DESCRIPTION OF EMBODIMENTS

FIGS. 1 and 2 show apparatus according to an embodiment of the presentdisclosure. The apparatus includes an acetabular cup impactor 1, adaptedto drive and implant an acetabular cup 11 into position at theacetabulum of a patient's pelvic bone 12, and an electronic device 2,the electronic device 2 being adapted to be located at a first locationon the pelvic region (see FIG. 1) and subsequently located at a secondlocation on the acetabular cup impactor 1 (see FIG. 2).

With reference also to FIG. 3, the electronic device 2 acts at least inpart as an orientation sensor through inclusion of a gyroscope 21, amagnetic field sensor 22 and an accelerometer 23 connected to aprocessor 24. In alternative embodiments, one or more of these sensorsmay be excluded. For example, the accelerometer 23 may be excluded orotherwise. The electronic device 2 further includes an input deviceconnected to the processor 24 that is in the form of a touch screendisplay 25, which touch screen display 25 also provides an output devicein conjunction with a speaker 26. A memory 27 is provided for datastorage and retrieval. In this embodiment, the electronic device 2 is aSmartphone, e.g. an iPhone™, although a variety of different electronicdevices may be used. Further, the sensors, processor, input and outputdevices need not be integrated into a single device. For example, in oneembodiment, the display and speaker may be maintained at a location thatis remote from the pelvic region and impactor, and may communicate withthe processor 24 via wires or wirelessly.

The acetabular cup impactor 1 includes a shaft 13 extending distallyfrom the acetabular cup/pelvic region, and a handle 14 at the distal endof the shaft. In this embodiment, when at the second location as shownin FIG. 2, the electronic device 2 is releasably fixed to the distal endof the handle 14 such that planar face of the electronic device, whichincludes the display 25, is fixed at an orientation that issubstantially orthogonal to the impactor shaft 13. A mount (not shown)is adapted to clamp the electronic device 2 to the handle 14. Theelectronic device 2 may be encased in a plastic covering. The plasticcovering may hermetically seal the electronic device 2.

The gyroscope 21, magnetic field sensor 22 and accelerometer 23 of theelectronic device provide in combination with the processor 24 anorientation sensor that can track orientation of the electronic device2, and hence the acetabular cup impactor 1 when mounted thereon. Bysensing movement of the electronic device 2 within the surroundinggravitational and magnetic fields, and optionally also acceleration anddeceleration of the device 2, changes in orientation about threeorthogonal axes of a coordinate system can be monitored.

In use, as part of a calibration process, the electronic device 2 ismounted at the first location on the pelvic region of the body as shownin FIG. 1. In particular, in this embodiment in which the patient is ina supine position, it is mounted so that its bottom edge substantiallylines up with a vector line extending between right and left anteriorsuperior iliac spines (ASIS) of the pelvic bone 12. In alternativeembodiments, the electronic device may be mounted so that its bottomedge is at a different angle to this vector line, such as a 45 degreeangle. In FIG. 1 and subsequent Figures, for simplicity, the pelvic boneof the patient is represented independently of any other body parts orbody tissue. In practice, other body parts and body tissue would, ofcourse, be present.

When the electronic device 2 is at the first location, the display 25 isadapted to display a pelvic calibration screen 3 as represented in FIG.4. Three touch-screen buttons are provided on the screen 3. One of thebuttons 31 enables input of the hip side of the patient, in particularso that a clinician or other use can indicate if the hip replacement isbeing carried out in relation to the left or right hip. Another of thebuttons 33 enables input of the positioning of the patient, inparticular so that the clinician or other user can indicate if thepatient is in a supine or a lateral orientation. Finally, a zero button32 is provided, which is to be pressed once the positioning of thepatient and hip side have been inputted, and once the electronic device2 is securely positioned at the first location (i.e. at the appropriatecalibration position). When the zero button 32 is pressed, theelectronic device 2 records its orientation, and hence the orientationof the pelvic region, and uses this as a reference orientation againstwhich all subsequent changes in orientation of the electronic device 2are compared.

After calibration (‘zeroing’), the electronic device 2 is transitionedfrom the first location on the pelvic region to the second location onthe impactor 1, in particular at the distal end of the handle 14 asshown in FIG. 2, where it displays an impactor orientation screen 4 asrepresented in FIG. 5. As it transitions from the calibration position,the electronic device 2 continually monitors changes in its orientationrelative to the reference orientation such that, when mounted on thehandle 14, it immediately knows its orientation, and hence theorientation of the impactor shaft 13, relative to the referenceorientation. The electronic device 2 can therefore display on the screen4 the orientation of the impactor shaft 13 relative to the referenceorientation (in terms of angle of anteversion 41 and angle ofinclination 42 in this embodiment) and it can monitor and update theorientation on the screen, as it moves with the impactor 1 thereafter.Thus, the clinician or other user can observe the angles of anteversionand inclination in ‘real-time’ on the display, allowing him/her to movethe acetabular cup impactor 1 to a desired orientation. The desiredorientation may be an angle of 20° anteversion and 45° inclination orotherwise. Once completed, or if recalibration of the referenceorientation is desired, a button 43 can be pressed to restart theprocedure.

Example mathematics that may be employed in this or other embodiments isset forth below, where:

RI=radiographic inclination pelvic reference frame

RA=radiographic anteversion pelvic reference frame

AI=anatomic inclination pelvic reference frame

AA=anatomic anteversion pelvic reference frame

ri=radiographic inclination gravity reference frame

ra=radiographic anteversion gravity reference frame

ai=anatomic inclination gravity reference frame

aa=anatomic anteversion gravity reference frame

y′−y=yaw

r=roll

P=pelvic roll

Assuming no pelvic roll:

Yaw gives radiographic inclination (RI)

Roll gives radiographic anteversion (RA)

To convert to anatomic anteversion (AA) and anatomic inclination (AI)per Murray (D. W. Murray: The definition and measurement of acetabularorientation. J Bone Joint Surg [Br] 1993; 75-B: 228-32):

Tan(AA)=Tan(RA)/Sin(RI)

Cos(AI)=Cos(RI)*Cos(RA)

Therefore:

Anatomic Anteversion=arctan(tan(r)/sin(y′−y))

Anatomic Inclination=arcos(cos(y′−y)*cos(r))

If there is pelvic roll ‘yaw’ is calculated about a vertical axis thathas rolled and roll calculated against the same axis.Supine position with pelvic roll to the right in a right hip:

AA−P=aa

AA=aa+P

AI=ai

ra=r

ri=y′−y

Cos(AI)=cos(ai)

=Cos(ri)*Cos(ra)

AI=arccos(cos(y′−y)*cos(r))

AA=arctan(tan(r)/sin(y′−y))+P

And for a left hip:

AI=arccos(cos(y−y′)*cos(r))

AA=arctan(tan(r)/sin(y−y′))−P.

In another embodiment of the present disclosure, the apparatus describedabove with reference to FIGS. 1 to 4 is adapted for use in trackingchanges in orientation of the pelvic region during surgery. Anelectronic device is mounted to the pelvis, e.g. as represented inFIG. 1. However, after carrying out a calibration process as describedwith reference to FIG. 4, the electronic device 2 is maintained inposition on the pelvic region and is used to track motion of the pelvicregion in at least two rotational axes (pitch (tilt) and roll) orpreferably three rotational axes (pitch, roll and yaw). The device 2 isadapted to display a pelvis tracking screen 5 as represented in FIG. 6,which presents the current orientation of the pelvis substantially in‘real-time’ during the surgical procedure. The electronic device 2 isadapted to record the pelvic movement in the memory 27 throughout thesurgical procedure. In one embodiment, predetermined limits on thedegree of motion of the pelvis are inputted by the clinician into theelectronic device 2, and an audible signal using the speaker 26 or othertype of alarm is provided as a warning when these limits are exceeded.

In yet another embodiment, the approach described with respect to thetwo preceding embodiments is combined through the provision of twoelectronic devices 2 a, 2 b. Referring to FIG. 7, a first one of theelectronic devices 2 a is used as described above to record a referenceorientation of the pelvic region prior to transitioning to the secondlocation where it determines the orientation of the impactor 1 relativeto the reference orientation. Further, a second one of the electronicdevices 2 b is used as described above to record a reference orientationof the pelvic region and is then maintained on the pelvic region totrack changes in orientation of the pelvic region during surgery. Thesecond electronic device 2 b is adapted to wirelessly communicate withfirst electronic device 2 a to provide information about changes in theorientation of the pelvic region, allowing correction of the referenceorientation recorded by the first electronic device 2 a to be madesubstantially in ‘real-time’.

FIG. 8 shows apparatus according to an embodiment of the presentdisclosure. The apparatus includes an acetabular cup impactor 10,adapted to drive and implant an acetabular cup 110 into position at theacetabulum of a patient's pelvic bone 120, and an electronic device 20,the electronic device 20 being mounted on the impactor 10. Withreference also to FIG. 10, the electronic device 20 includes an imagecapture device in the form of a video camera 210, a digital display 220,a tilt sensor 230, a processor 240, a touch keypad 250 and a memory 260for data storage and retrieval. In this embodiment, the electronicdevice 20 is a Smartphone, e.g. an iPhone™, although a variety ofdifferent electronic devices may be used. The camera 210, display 220,tilt sensor 230 and processor 240 need not be integrated into a singledevice 20, nor mounted on the impactor 10. For example, in oneembodiment, the display and/or processor may be located remotely fromthe impactor 10.

The electronic device 20 is releasably fixed to the shaft 130 of theimpactor 10 via a mount 30 such that the camera of the electronic devicefaces the pelvic bone 120 and, more generally, the pelvic region of thepatient. The mount 30 is adapted to clamp to the shaft 130 of theimpactor 10 through provision of a sleeve portion 310 that at leastpartially extends around the impactor shaft 130. The mount 30 is alsoadapted to clamp to the electronic device 20 through provision of one ormore arms 320 that project from the sleeve portion 310 and abut opposingsides or edges of the electronic device 20. The electronic device 20 maybe encased in a plastic covering. The plastic covering may hermeticallyseal the electronic device 20.

The camera 210 of the electronic device 20 is adapted to sequentiallycapture a plurality of images of the pelvic region of the patient (i.e.video the pelvic region of the patient), and the images are presented,substantially in ‘real time’, on the display 220. The pelvis 120includes a first marker 140 thereon, more particularly a vector line 140extending between right and left anterior superior iliac spines (ASIS)121 that is imagined or drawn on bone and/or tissue between ASIS 121.With reference to FIG. 9, which shows an example image (frame) 270 aspresented on the display 220, the ASIS vector line 140 is represented inthe image 270. In FIG. 8 and subsequent Figures, for simplicity, thepelvic bone 120 of the patient is represented independently of any otherbody parts or body tissue. In practice, other body parts and body tissuewould, of course, be present.

The processor 240 of the electronic device 10 is adapted to receiveorientation data related to the impactor 10 (and the acetabular cup110). In this embodiment, the patient is located in a supine position,and the orientation data received by the processor 240 includes adesired inclination angle for the impactor and measured anteversionangles for the impactor. The desired inclination angle, which is 45° inthis example, is input into the electronic device 20 using thetouchscreen keypad 250. The anteversion angle is continually measuredusing the tilt sensor of the electronic device 20.

Based on the received orientation data, and with reference to FIGS. 13and 14, the processor 240 is adapted to overlay one or more secondmarkers, more particularly alignment lines 271 a-e, in images 270 a, 270b displayed by the display device 220 such that, when the ASIS vectorline 140, as seen in the images, is substantially aligned with one ormore of the alignment lines 271 a-271 e, the acetabular cup impactor 10will be oriented at the desired angle of inclination.

In order to provide this guidance for the inclination angle, theprocessor 240 is adapted to determine the appropriate orientation forthe plurality of alignment lines 271 a-e, when overlaid at respectivepositions in the images 270. The appropriate orientation of thealignment lines 271 a-e, when overlaid in the images, is partiallydependent on the position in the images at which they are to beoverlaid, due to the angular range of the field of view of the camera.This means that the orientations of items as seen within images, such asthe ASIS vector line 140, are dependent not only on their actualorientation relative to the impactor 10, but on where in the field ofview of the camera those items are positioned.

In this embodiment, the processor 240 is adapted to overlay fivealignment lines 271 a-e in the images 270 a, 270 b in accordance withequally spaced angular distances along the vertical axis of the field ofview of the camera 210. In this embodiment, the camera 210 has a fieldof view of about 50° to 60° and the alignment lines are located, andtheir orientation determined, with respect to angular distances in thevertical axis of −20°, −10°, 0°, +10° and +20°, from the centralhorizontal axis of the camera's field of view. These angular distancesare represented by guidelines 272 a-e in FIG. 11, where FIG. 11 shows anoutline 273 of the area covered by the image 270 of FIG. 9.

Using Equation 1, the processor 240 is adapted to determine for eachangular distance (d) from the central horizontal line within the fieldof view of the camera, and for a measured anteversion angle (x) and adesired inclination angle (y), the angle (g) at which to orientalignment lines 271 a-e that are to be overlaid in the images presentedon the display.

tan g=tan(y)·sin(x+d)  Equation 1

Example orientations for the alignment lines 271 a-e as determined usingEquation 1 for each of the angular distances (d) are represented in FIG.12, each alignment line 271 a-e being overlaid next to a respectiveguideline 272 a-272 e. The orientations angles (g) can continuallychange as a result of the measured anteversion angle (x) changing asindicated above, and thus the alignment lines 271 a-e can be seen torotate within the screen as the impactor 1 is moved.

FIG. 13 shows a first image 270 a as seen on the display by the surgeon,when the alignment lines 271 a-271 e have been overlaid by the processor240. In the corner of the image 270 a, the measured anteversion angle274 is presented and continually updated as the impactor 10 moves.

The desired angle of inclination of the impactor 10 is achieved when theASIS vector line 140 is substantially aligned with the nearest alignmentline or lines 271 a-e. In FIG. 13, the vector line 140 can be seen inimage 270 a positioned nearest the top two alignment lines 271 a, 271 b.The vector line 140 is substantially misaligned with these alignmentlines 271 a, 271 b. This indicates that the impactor 10 is not at thedesired angle of inclination. Furthermore, the anteversion angle 274 aspresented on the display is at 23°, rather than a desired angle of 20°.

However, through movement of the impactor 10, and observation of thedisplay 220, the surgeon can move the impactor 10 to a position asrepresented in the image 270 b of FIG. 14. In this image 270 b, thevector line 140 is substantially aligned (i.e. substantially parallel)with the nearest alignment lines 271 a, 271 b and the anteversion angle274 as presented on the display is at the desired angle of 20°. At thispoint, the desired orientation of the impactor 10, and thus theacetabular cup 110 connected to the impactor 10, is achieved.

As indicated, in this embodiment, the patient is in a supine position.However, the approach described above can be carried out, mutatismutandis, with a patient in the lateral recumbent position. In thisvariation, the tilt sensor will provide the angle of inclination of theimpactor, and the alignment lines will be used instead to arrive at thedesired angle of anteversion. More particularly, when the ASIS vectorline, as seen in the images, is substantially aligned with one or moreof the alignment lines, the acetabular cup impactor will be oriented atthe desired angle of anteversion.

Equation 2 can be utilised in place of Equation 1. In particular usingEquation 2, the processor is adapted to determine for each angulardistance (d) from a central horizontal line within the field of view ofthe camera, and for a measured inclination angle (y) and a desiredanteversion angle (x), the angle (g) at which to orient alignment linesthat are to be overlaid in the images presented on the display.

tan g=tan(x)·sin(y+d)  Equation 2

FIG. 15 shows apparatus according to another embodiment of the presentdisclosure. The apparatus includes an acetabular cup impactor 10,adapted to drive and implant an acetabular cup 110 into position at theacetabulum of a patient's pelvic bone 120, and an electronic device 200,the electronic device 200 being mounted to the pelvic region, e.g. onthe pelvic bone 120. With reference also to FIG. 17, the electronicdevice 200 includes an image capture device in the form of a videocamera 201, a digital display 202, a processor 203, a touch keypad 204and a memory 205 for data storage and retrieval. A tilt sensor may alsobe included. In this embodiment, the electronic device 200 is a tablet,e.g. an iPad™ although a variety of different electronic devices may beused. The camera 201, display 202, and processor 203 need not beintegrated into a single device 200, nor all mounted on the pelvicregion. For example, in one embodiment, the display and/or processor maybe located remotely from the pelvic region.

The electronic device 200 is releasably fixed to the pelvic bone 120 orpelvic region via a mount (not shown) such that the camera 201 of theelectronic device 200 faces the impactor 10. The electronic device 200may be encased in a plastic covering. The plastic covering mayhermetically seal the electronic device 200.

The camera 201 of the electronic device 200 is adapted to sequentiallycapture a plurality of images of the impactor 10 and the images arepresented substantially in ‘real time’ on the display 202.

A navigation element 40 in the form of two circular disks 410, 420,connected together by a spacer 430, is releasably mounted to the distalend of the impactor 10. The two disks 410, 420 are concentric and thecentres of the disks 410, 420 are aligned with the longitudinal axis ofthe impactor 10. The disk 410 closest to the impactor 10 has a smallerdiameter than the disk 420 furthest from the impactor 10. The edges 401,402 of the disks define circles that provide two first markers. Withreference to FIG. 16, which shows an example image (frame) 206 aspresented on the display 202, the two first markers 401, 402 are visiblein the image 206.

The processor 203 of the electronic device 200 is adapted to receiveorientation data related to the impactor 10 (and the acetabular cup110). In this embodiment, the patient is located in a supine position,and the orientation data received by the processor includes a desiredinclination angle and a desired anteversion angle for the impactor. Thedesired inclination and anteversion angles, which are 45° and 20°,respectively, in this example, are input into the electronic device 200using the touchscreen keypad 204.

In this embodiment, a calibration procedure is performed to determinethe pivot point of the impactor 10 relative to the camera 201 and thepositions of the first markers along the longitudinal axis of theimpactor 10. With reference to FIG. 18a , during the calibrationprocedure the processor 203 is adapted to overlay a third marker 208 ina first position in images 206 a displayed by the display device 202.The impactor 10 is then moved by a surgeon, generally in a direction asindicated by arrow 209, such that one of the disks, in particular thelarger disk 402 in this embodiment, is aligned with the third marker208. Once aligned, the user is required to touch the screen, or ‘click’a cursor on the screen, at the position in the image at which the otherof the disks, in particular the smaller disk 401 in this embodiment, islocated. This process is repeated for a number of different positions(e.g. second to fourth positions) of the third marker 209, asrepresented in images 206 b-206 d of FIGS. 18b to 18d . This enables adetermination to be made of the exact and relative positions of the twofirst markers 401, 402 in the images 206 a-206 d, and throughapplication of trigonometric functions, calibration data including thepivot position of the impactor relative to the camera, and the positionsof the first markers along the longitudinal axis of the impactor, canalso be determined.

Based on the calibration data and the received orientation data (i.e.the desired inclination and anteversion angles), the processor 203 isadapted to determine where in the displayed images a second marker 211should be located to guide the impactor so that it has the desiredinclination and anteversion angles. In this embodiment, with referenceto FIG. 19, the processor 203 is adapted to overlay the second marker211 in the images 206 e displayed by the display device 202 such that,when the larger disk 402, as seen in the images, is substantiallyaligned with the second marker 211, the acetabular cup impactor 10 willbe oriented at the desired orientation.

In a variation of this embodiment, the processor is adapted to usefeature detection to determine the positions and shapes of the firstmarkers 401, 402 within the images 206. The feature detection may beused in place of a user being required to touch or ‘click’ on theposition of one of the first markers 401, in order to identify theposition of that marker. Alternatively, feature detection may be used toremove the need for the calibration procedure entirely.

In more detail, to the extent that the centre of the camera 201 ismisaligned with the longitudinal axis of the impactor 10, the firstmarkers 401, 402 will appear as ellipses in the images 206. The shape(e.g. minor to major axis ratio) and relative positioning of theellipses is dependent on the angle at which the impactor 10 is located.Following from this, feature detection can be used to determine theinclination and anteversion angles for the impactor 10, and these anglescan be presented by the processor 203 substantially in ‘real time’ onthe images 206, e.g., within boxes 2011 a, 2011 b in the image 206 asshown in FIG. 16. This enables a surgeon to move the impactor 10 to thedesired orientation based on observation of changes to the displayedangles. Alternatively or additionally, based on the feature detectionand user input of the desired inclination and anteversion angles, asecond marker can be overlaid on the images to guide movement of theimpactor 10 to the desired orientation.

With reference to FIG. 20, in an alternative embodiment, apparatus isprovided that is substantially identical to the apparatus shown in FIG.15, but which employs a different type of navigation element, inparticular a navigation element in the form of a sphere 400 that isreleasably mounted at the distal end of the impactor 10. The sphere 400provides a first marker. With reference to FIG. 21, which shows anexample image (frame) 212 as presented on the display, the first marker400 is visible in the image 212.

Again, in this embodiment, a calibration procedure is performed todetermine the pivot point of the impactor relative to the camera 201,and the positions of the first marker 400 along the longitudinal axis ofthe impactor 10. With reference to FIG. 22a , during the calibrationprocedure the processor 203 is adapted to overlay a third marker 213 ina first position in images 212 a displayed by the display device. Theimpactor 10 is then moved by the surgeon, generally as indicated byarrow 214, such that the first marker 400 is aligned with the thirdmarker 213. Once aligned, the user is required to touch the screen, or‘click’, at one of a plurality of guidelines 215 a-215 e that areoverlaid on the screen, which guideline 215 a-215 e has the closestangular relationship to the angle of extension of the shaft 130 as seenwithin the image 212 a. This process is repeated for a number ofdifferent positions (e.g. second to fourth positions) of the thirdmarker 213, as represented in images 212 b-212 d of FIGS. 22b to 22d .This enables a determination to be made of the positioning of the firstmarker 400 and the angle of extension of the shaft 130 of the impactor10 within the images, and through application of trigonometricfunctions, calibration data including the pivot position of the impactorrelative to the camera, and the positions of the first marker along thelongitudinal axis of the impactor, can also be determined.

Based on the calibration data and the received orientation data (i.e.the desired inclination and anteversion angles), the processor 203 isadapted to determine where in images a second marker 216 should belocated to guide the impactor 10 so that it has the desired inclinationand anteversion angles. In this embodiment, with reference to FIG. 23,the processor 203 is adapted to overlay the second marker 216 in theimages 212 e displayed by the display device 22 such that, when thesphere 400, as seen in the images, is substantially aligned with thesecond marker 216, the acetabular cup impactor 10 will be oriented atthe desired orientation.

While the use of navigation elements, feature detection, and calibrationsteps, etc., is described in conjunction with FIGS. 15 to 23, where theimage capture device is mounted to the pelvic region, substantially thesame navigation elements, feature detection, and calibration steps,etc., may be employed, mutatis mutandis, when the image capture deviceis mounted on the impactor 10, e.g. as shown in FIG. 8. In thisvariation, navigation elements similar to those described in FIGS. 15 to23 may be mounted on the pelvic region, for example.

It will be appreciated by persons skilled in the art that numerousvariations and/or modifications may be made to the above-describedembodiments, without departing from the broad general scope of thepresent disclosure. The present embodiments are, therefore, to beconsidered in all respects as illustrative and not restrictive.

1-57. (canceled)
 58. A method of determining an orientation of anacetabular cup impactor, comprising: recording a reference orientationof a patient's pelvic region using an electronic orientation sensorlocated at a first location on the patient's pelvic region, wherein inthe first location the electronic orientation sensor is not coupled witha mechanical device while the mechanical device is engaged within anacetabulum of the patient, and monitoring an orientation of anacetabular cup impactor relative to the reference orientation using theelectronic orientation sensor when the electronic orientation sensor islocated at a second location on the acetabular cup impactor after beingtransitioned to the second location from the first location, theacetabular cup impactor being moveable to a desired orientation relativeto the patient's pelvic region for implantation of an acetabular cupinto the acetabulum.
 59. The method of claim 58, further comprisingengaging the orientation sensor and the pelvic region with a first mountto releasably fix the positions of the orientation sensor and the pelvicregion relative to each other when the orientation sensor is located atthe first location.
 60. The method of claim 58, further comprisingengaging the orientation sensor and the impactor with a second mount toreleasably fix the positions of the orientation sensor and the impactorrelative to each other when the orientation sensor is located at thesecond location.
 61. The method of claim 58, wherein monitoring theorientation of the acetabular cup impactor relative to the referenceorientation comprises monitoring the orientation in three-dimensionalspace.
 62. The method of claim 61, wherein monitoring the orientation ofthe acetabular cup impactor relative to the reference orientationcomprises monitoring an angle of anteversion and an angle inclination ofthe acetabular cup impactor.
 63. The method of claim 58, furthercomprising providing the monitored orientation of the impactor or therecorded reference orientation to a clinician or other user.
 64. Themethod of claim 63, wherein providing the monitored orientation of theimpactor or the recorded reference orientation comprises displaying theorientation of the impactor or the recorded reference orientation on adisplay.
 65. The method of claim 64, wherein the display is comprised inthe electronic orientation sensor.
 66. The method of claim 58, whereinthe orientation sensor is comprised in a smartphone or a tabletcomputer.
 67. The method of claim 58, wherein the monitored orientationor the reference orientation is determined using one or more of anaccelerometer, a magnetic field sensor and a gyroscope comprised in theorientation sensor.
 68. A non-transitory computer readable storagemedium having stored thereon instruction which, when executed, cause aprocessor to perform a method comprising: recording a referenceorientation of a patient's pelvic region using an electronic orientationsensor located at a first location on the patient's pelvic region,wherein in the first location the electronic orientation sensor is notcoupled with a mechanical device while the mechanical device is engagedwithin an acetabulum of the patient, and monitoring an orientation of anacetabular cup impactor relative to the reference orientation using theelectronic orientation sensor when the electronic orientation sensor islocated at a second location on the acetabular cup impactor after beingtransitioned to the second location from the first location, theacetabular cup impactor being moveable to a desired orientation relativeto the patient's pelvic region for implantation of an acetabular cupinto the acetabulum.